Post on 23-Dec-2015
Forecasting Tropical cyclones
Regional Training Workshop on Severe Weather Forecasting and Warning Services
(Macao, China, 9 April 2013)
Contents
1. Outline of TC forecasting process
2. TC Analysis
3. TC Forecasting
4. Verification of TC forecast and models
Outline of TC forecasting process
Reanalysis
Operational process
Forecast products
Best track
Forecast Models
Observations SYNOP,SHIP Radar Satellite, etc.
Verification
Forecasting
Analysis
Outline of TC forecasting process
Operational TC analysis and Forecasting
1. TC Analysissatellite observations (Dvorak Method)surface observationsradar observations (only position)
2. TC ForecastingNWP modelsPersistence (for very short-term forecast)
Contents
1. Outline of TC forecasting process
2. TC Analysis
3. TC Forecasting
4. Verification of TC forecast and models
TC Analysis
Analysis of current position and intensitysatellite observationssurface observationsradar observations (position only)
TC analysis is important for TC forecasting.
With a wrong TC analysis of current position and intensity, TC forecast will be wrong even if the NWP model performance is excellent.
TC Analysis
microwave image (35GHz & 85GHz) available when satellites hit a cyclone
GCOM-W1
From JAXA webpage
DMSP Series
From NASA webpage
TRMM
From JAXA webpage
IR & VIS image provided every 30 min. by MTSATMTSA
T
TC Analysis
Observations such as SYNOP/SHIP/BUOY
TC Analysis
Naha
Radar image
TC Analysis
Satellite image (Dvorak method)cloud
patternintensity
TC Analysis
01)(
rr
PPrP
0
Exponential ordinate
= Takahashi’s diagramNormal ordinate
Estimate of pressure profile of a tropical cyclone
TC Analysis
Estimate of pressure profile of a tropical cyclone(0) This method is available if you can determine TC Center accurately.
(1) Measure the distance from TC Center to SYNOP data A on the weather map.
(2) Plot the point A which show the observed pressure (PA) and distance from the TC center (rA) on the pressure profile chart.
(3) Same processes (1) & (2), plot B, C…
(4) Draw a linear regression line on the pressure profile chart, then extrapolate the line to the TC center for estimating PCN.
PC
PA
B
C
PB
rC rA
rB
A
PCN
TC Analysis
Estimate of 30-kt/50-kt wind area
Contents
1. Outline of TC forecasting process
2. TC Analysis
3. TC Forecasting
4. Verification of TC forecast and models
TC Forecasting
Forecasting track and intensity
Based on NWP modelsDeterministic model (GSM)Ensemble system (TEPS)Consensus method (average of various models)Multi ensemble system PersistenceNote:valid only for short-term forecastsmall scale oscillations leads to wrong
interpretations.
Models Forecast Range
Global ModelGSM TL959 L60about 20 km in horizontal,
60 layers
FT= 84h (00,06,18UTC)FT=216h (12 UTC)
Mesoscale Model
MSMabout 5 km in horizontal, 50 layers
FT=15h (00, 06, 12, 18UTC)FT=33h (03, 09, 15, 21UTC)
One-week EPSGSM TL319 L60 M51about 60km in horizontal, 60 layers
FT=216h (12UTC)
Typhoon EPSGSM TL319 L60 M11about 60km in horizontal, 60 layers
FT=132h (00, 06, 12, 18UTC)
medium range forecast
short range forecast
one-week forecast
tropical cyclone forecast
JMA NWP models
NWP Model outputs
3-day forecast
5-day track forecast
TC forecasting based on NWP models
TC forecasting (track)
Track forecast
1. Center position forecast
2. Radius of probability circle
TC forecasting (track)
1. Center position forecast
main: GSM and TEPS reference: One-Week EPS, ECMWF, ECMWF EPS
TC forecasting (track)
2. Radius of probability circle (PC)
PC shows uncertainty of track forecast.
radius of PC is based on verification of recent track forecast.
PC decision method is different between 72-hour forecast and 120-hour forecast.
TC forecasting (track)
(1) 24, 48 and 72-hour forecast
FT speed direction
V≦10kt
10kt<V ≦30kt
30kt<V
24NW (260-359) 70 75
130Other (360-259) 85 85
48NW (260-359) 110 140
210Other (360-259) 160 180
72NW (260-359) 160 210
325Other (360-259) 220 250
Unit: nm
NW
other
PC radius depends on forecasted TC movement based on the verification of TC track forecast in 2004 to 2007.
2. Radius of probability circle
TC forecasting (track)
PC radius depends on ensemble spread of TEPS
based on verification of track forecasts in 2007-2008.
2. Radius of probability circle
(2) 96 and 120-hour forecast
Tracks of TEPS members Pink track: ensemble mean track Black track: GSM track
6-hourly accumulated ensemble spread (km) (2007-2008)
Ensemble spread
TC forecasting (track)
Our verification result says that the radius of 70% probability circle enlarges in proportion to ensemble spread.
FT Group A Group B Group C
96 200 280 425
120 250 375 500
Unit: nautical mile
2. Radius of probability circle
(2) 96 and 120-hour forecast
TC forecasting (Intensity)
Intensity forecast
1. Central pressure (CP)
2. Maximum sustained wind (MSW)
3. Peak gust
4. Storm warning area
Operational TC forecast
Model output and the guidance
Time
Central Pressure
A A A
AG G G
G
GSM prediction
Analysis
MM M M
M
termination of adjustment (FT=36)
Initial intensity adjustment
present forecast time
M
GG
M
GSM guidance
G G
1. Central Pressure(CP)
Operational TC forecast
Statistical development curve
1. Central Pressure (CP)
Operational TC forecast
2. & 3. Forecast of MSW & peak gust
MSW conversion from CP
Peak gust MSW x 1.4
CP
MSW
Statistical method
Operational TC forecast
4. Forecast of Storm warning area
50-kt wind radius (converted from CP) + PC radius
Cen
tral P
ressu
re (
hP
a)
50kt wind radius (NM)
Standard
Large
Small
CP
50kt-wind radius
Storm Warning Area
50-kt wind radius
PC radius
Statistical method
Operational TC forecast
4. Forecast of Storm warning area
Developing stage Mature stage
Contents
1. Outline of TC forecasting process
2. TC Analysis
3. TC Forecasting
4. Verification of TC forecast and models
Verification of TC forecast and models
Position errors of track forecasts in 2011
Verification of TC forecast and models
Position errors of GSM in 2011
Verification of TC forecast and models
FT=48 FT=72
Position errors of GSM in 2011
direction of movement
Verification of TC forecast and models
Intensity errors of GSM in 2011
Developing stage
develop more slowly than analysis
Weakening stage
development persists in many cases
Verification of TC forecast and models
Position errors of TEPS in 2011
Verification of TC forecast and models
example of model outputs: Nock-ten (1108) 26 Jul, 12UTC Initial
Verification of TC forecast and models
example of track forecast: Nock-ten (1108) 26 Jul, 18UTC Initial
Verification of TC forecast and models
example of model outputs: Nanmadol (1111) 24 Aug, 12UTC Initial
Verification of TC forecast and models
example of track forecast : Nanmadol (1111) 24 Aug, 18UTC Initial
End